Controller and control method for internal combustion engine

ABSTRACT

To provide a controller and a control method for an internal combustion engine capable of calculating a target value of controlled variable of internal combustion engine which realizes the target torque, while reducing the number of calculations using a torque characteristics function. A controller and a control method for an internal combustion engine calculates ignition sample numbers of ignition corresponding torques corresponding to the respective ignition sample numbers of ignition timings, by using a torque characteristics function relationship in which a relationship between driving condition and output torque is preliminarily set; and calculates an ignition torque approximated curve approximating a relationship between the ignition sample numbers of the ignition timings and the ignition sample numbers of the ignition corresponding torques; and calculates a target ignition timing corresponding to the target torque.

INCORPORATION BY REFERENCE

This is a divisional application of U.S. patent application Ser. No.16/257,378, filed Jan. 25, 2019, in the U.S. Patent and TrademarkOffice, which application claims priority from Japanese PatentApplication No. 2018-30340 filed on Feb. 23, 2018 including itsspecification, claims and drawings, both of which prior applications areincorporated herein by reference in their entirety.

BACKGROUND

The present disclosure relates to a controller and a control method foran internal combustion engine for controlling the internal combustionengine by setting output torque as control objective.

Recently, a controller and a control method for the internal combustionengine has been proposed to use an output torque of the internalcombustion engine which is a physical value acting on vehicle controldirectly, as a request value of the internal combustion engine outputreceived from a driver and each vehicle system (motor control for hybridvehicle, transmission control, brake control, traction control, and thelike); and to determine air amount, fuel amount, ignition timing, andthe like which are controlled variables of the internal combustionengine by setting the output torque as a target value of the internalcombustion engine output; and to realize cooperative control and obtaingood travel performance by estimating actual output torque based on theactual driving conditions of internal combustion engine and transmittingto each vehicle system.

Although such a control method is generally called torque base control,in this control method, it is important that the actual output torquecan be calculated with good accuracy based on the driving conditions ofinternal combustion engine. If this can be achieved, by inversecalculation of this, target values of the controlled variables ofinternal combustion engine (for example, a throttle opening degree, anEGR opening degree, an ignition timing, an air-fuel ratio, and the like)can be calculated from the target torque.

For example, in JP 5644733 B, as the target torque in torque basecontrol, there are a low response target torque and a high responsetarget torque which are different in response. In JP 5644733 B,operation of air amount such as throttle control is performed so as torealize the low response target torque, and operation of ignition timingor fuel injection amount is performed so as to realize the high responsetarget torque. In more detail, MBT ignition timing to the drivingcondition of the internal combustion engine, a thermal efficiency inMBT, a reduction rate of torque to a retard amount from MBT, and thelike are stored in many map data; further, correction by an EGR amountand an air-fuel ratio is performed if needed; by combining these, acalculation of actual torque and a control capable of corresponding to alow response target torque and a high response target torque areconfigured.

Also in JP 4499809 B, there are first target torque for performing atorque control by a throttle opening degree, and second target torquefor performing a torque control by ignition timing; and calculationwhich uses many map data is performed in order to calculate a targetintake air amount and a target ignition timing from these targettorques.

By the way, as a method to estimate the output torque from the drivingcondition of the internal combustion engine, besides the abovecalculation method using the map data, a method adapting a neuralnetwork technology like JP H11-351045 A is also proposed, for example.Here, the neural network is the mathematical model which aimed atexpressing several characteristics observed in the brain function bysimulation on a computer. By making a feedforward propagation typeneural network (FNN: Feedforward Neural Network) learn previously usingoutput value to input values as teacher data, it can be used as ageneral-purpose approximation function which simulates a relationbetween the input values and the output value which were learned. As alearning method of the neural network, the error back propagation method(back propagation method) is generally known.

SUMMARY

To a mechanism for internal combustion engine control which becomescomplex for recent improvement in fuel efficiency, an internalcombustion engine control system also becomes complex similarly, and anincrease of the adaptation man hours becomes a large problem. As anexample of the mechanism for internal combustion engine control whichbecomes complex, the intake and exhaust VVT (Variable Valve Timing), avariable valve lift, the variable compression ratio, a turbocharger, aswirl control valve, a tumble control valve, and the like are known. Inthe case of the control method using map data as JP 5644733 B or JP4499809 B, if the mechanism for internal combustion engine controlbecomes complex, many map data is required correspondingly, andaccordingly, the adaptation man hours also increase. In a viewpoint ofan experiment of internal combustion engine necessary for adaptation, acommercially available MBC (Model Based Calibration) tool has beendeveloped in recent years. For example, as shown in “Application ofmodel base calibration in direct injection diesel engine”, MotonoriYoshida, the Mazda Motor technical report, No. 24 (2006), in this tool,a test plan of internal combustion engine is planned based on DOE(Design of Experiments), data collection is performed in conjunctionwith a testing equipment of internal combustion engine, a statisticmodel of internal combustion engine is created from its result, and amap data used for control based on this model is created.

However, although map data can be created by MBC tool, in order tocreate many map data, corresponding man hours are required and many manhours are required also for managing its data for every model of theinternal combustion engine. Furthermore, if the map data for control iscreated from the statistic model of MBC tool, since it is consideredthat the number of parameters of the driving condition of internalcombustion engine which can be considered is decreased and accuracy isdeteriorated, many man hours are required also for checking of controlaccuracy using this map data and fine tuning. In this way, in theconventional map control, even though MBC tool is introduced, there is aproblem that still enormous adaptation man hours are required.

About the method to estimate the output torque from the drivingcondition of internal combustion engine using the feedforwardpropagation type neural network (FNN) like JP H11-351045 A, in theconventional method only with one middle layer, there is a problem thatsufficient accuracy cannot be obtained even if FNN is used as theapproximation function. In the viewpoint of approximate precision, amethod called deep learning is known in recent years. For example, bymulti-layering (deep layering) the neural network similar to theconventional one, this method can improve accuracy as the approximationfunction significantly. While learning could not be well performed dueto the vanishing gradient problem and the like in the conventionallearning method, learning came to be well performed by developed variouslearning techniques in recent years. This deep learning is known also asthe one method of the artificial intelligence (AI) and the machinelearning which attract attention in recent years.

Then, if the output torque is estimated from the driving condition ofinternal combustion engine using FNN as the approximation function, itis considered that by creating teacher data with MBC tool and learningit, the output torque can be well estimated by minimum adaptation manhours. Furthermore, since a neural network may be used as one of themethods of creating the statistical model of internal combustion enginealso in MBC tool, the output torque can also be estimated from thedriving condition of internal combustion engine using the statisticalmodel of internal combustion engine itself created by MBC tool, in thiscase, man hours are further reduced.

However, the output torque is just estimated as it is, the targetignition timing and the target intake air amount which realize the lowresponse target torque and the high response target torque cannot becalculated. For example, as shown in “Machine learning professionalseries deep learning”, Takayuki Okaya, Kodansha, 2015, if an ignitiontiming or an intake air amount is changed little by little and theoutput torque is calculated repeatedly using a function such as FNN, atarget ignition timing or a target intake air amount which realizes thetarget torques can be searched. However, if the calculation using thefunction such as FNN is performed repeatedly, arithmetic load isincreased. Especially, if system structure becomes complex and thefunction such as FNN becomes complex, arithmetic load is increasedsignificantly. Therefore, it is desired to lower the number ofcalculations using the function such as FNN as much as possible.

Thus, it is desired to provide a controller and a control method for aninternal combustion engine capable of calculating a target value ofcontrolled variable of internal combustion engine which realizes thetarget torque, while reducing the number of calculations using a torquecharacteristics function and the like which expresses a characteristicsof the output torque to driving condition as much as possible.

A first controller for an internal combustion engine according to thepresent disclosure including:

a plural ignition torque calculation unit that calculates ignitionsample numbers of ignition corresponding torques which are the ignitionsample numbers of output torques corresponding to the respectiveignition sample numbers of ignition timings which are preliminarily setto plural numbers, by using a torque characteristics function in which arelationship between preliminarily set kinds of driving conditionsincluding an ignition timing and the output torque of the internalcombustion engine is preliminarily set;

an ignition torque approximated curve calculation unit that calculatesan ignition torque approximated curve which is an approximated curveapproximating a relationship between the ignition sample numbers of theignition timings and the ignition sample numbers of the ignitioncorresponding torques;

an approximated curve ignition calculation unit that calculates theignition timing corresponding to a target torque which is an outputtorque required for the internal combustion engine, as a target ignitiontiming, by using the ignition torque approximated curve; and

an ignition control unit that performs energization control to anignition coil, based on the target ignition timing.

A second controller for an internal combustion engine according to thepresent disclosure including:

a driving condition detection unit that detects driving conditions ofthe internal combustion engine including in-cylinder intake air amountinformation which is information of an air amount taken into acombustion chamber;

a plural intake ignition calculation unit that calculates intake samplenumbers of basic values of target ignition timing corresponding to therespective intake sample numbers of the in-cylinder intake air amountinformations which are preliminarily set to plural numbers, by using anignition timing setting function in which a relationship betweenpreliminarily set kinds of driving conditions including the in-cylinderintake air amount information, and the basic value of target ignitiontiming is a preliminarily set;

a plural intake torque calculation unit that calculates the intakesample numbers of intake ignition corresponding torques which are theintake sample numbers of output torques corresponding to the respectiveintake sample numbers of the in-cylinder intake air amount informationsand the respective intake sample numbers of the basic values of targetignition timing, by using a torque characteristics function in which arelationship between preliminarily set kinds of driving conditionsincluding the in-cylinder intake air amount information and an ignitiontiming, and the output torque of the internal combustion engine is apreliminarily set;

an intake torque approximated curve calculation unit that calculates anintake torque approximated curve which is an approximated curveapproximating a relationship between the intake sample numbers of thein-cylinder intake air amount informations and the intake sample numbersof the intake ignition corresponding torques;

a target intake air amount calculation unit that calculates thein-cylinder intake air amount information corresponding to the targettorque which is an output torque required for the internal combustionengine, as a target in-cylinder intake air amount information, by usingthe intake torque approximated curve; and

an intake air amount control unit that controls the air amount takeninto the combustion chamber, based on the target in-cylinder intake airamount information.

A first control method for an internal combustion engine according tothe present disclosure including:

a plural ignition torque calculation step that calculates ignitionsample numbers of ignition corresponding torques which are the ignitionsample numbers of output torques corresponding to the respectiveignition sample numbers of ignition timings which are preliminarily setto plural numbers, by using a torque characteristics function in which arelationship between preliminarily set kinds of driving conditionsincluding ignition timing and an output torque of the internalcombustion engine is preliminarily set;

an ignition torque approximated curve calculation step that calculatesan ignition torque approximated curve which is an approximated curveapproximating a relationship between the ignition sample numbers of theignition timings and the ignition sample numbers of the ignitioncorresponding torques;

an approximated curve ignition calculation step that calculates theignition timing corresponding to a target torque which is an outputtorque required for the internal combustion engine, as a target ignitiontiming, by using the ignition torque approximated curve; and

an ignition control step that performs energization control to anignition coil, based on the target ignition timing.

A second control method for an internal combustion engine according tothe present disclosure including:

a driving condition detection step that detects driving conditions ofthe internal combustion engine including in-cylinder intake air amountinformation which is information of an air amount taken into acombustion chamber;

a plural intake ignition calculation step that calculates intake samplenumbers of basic values of target ignition timing corresponding to therespective intake sample numbers of the in-cylinder intake air amountinformations which are preliminarily set to plural numbers, by using anignition timing setting function in which a relationship betweenpreliminarily set kinds of driving conditions including the in-cylinderintake air amount information, and the basic value of target ignitiontiming is a preliminarily set;

a plural intake torque calculation step that calculates the intakesample numbers of intake ignition corresponding torques which are theintake sample numbers of output torques corresponding to the respectiveintake sample numbers of the in-cylinder intake air amount informationsand the respective intake sample numbers of the basic values of targetignition timing, by using a torque characteristics function in which arelationship between preliminarily set kinds of driving conditionsincluding the in-cylinder intake air amount information and ignitiontiming, and the output torque of the internal combustion engine is apreliminarily set;

an intake torque approximated curve calculation step that calculates anintake torque approximated curve which is an approximated curveapproximating a relationship between the intake sample numbers of thein-cylinder intake air amount informations and the intake sample numbersof the intake ignition corresponding torques;

a target intake air amount calculation step that calculates thein-cylinder intake air amount information corresponding to the targettorque which is an output torque required for the internal combustionengine, as a target in-cylinder intake air amount information, by usingthe intake torque approximated curve; and

an intake air amount control step that controls the air amount takeninto the combustion chamber, based on the target in-cylinder intake airamount information.

According to the first controller and the first control method for theinternal combustion engine, without performing the calculation using thetorque characteristics function repeatedly to search the ignition timingcorresponding to the target torque directly, the approximated curve iscalculated based on the ignition sample numbers of calculation resultsof the torque characteristics function, and the ignition timingcorresponding to the target torque is calculated using the approximatedcurve, therefore the calculation using the torque characteristicsfunction can be reduced to the preliminarily set ignition samplenumbers.

According to the second controller and the second control method for theinternal combustion engine, without performing the calculation using thetorque characteristics function and the ignition timing setting functionrepeatedly to search the charging efficiency corresponding to the targettorque directly, the approximated curve is calculated based on theintake sample numbers of calculation results of the torquecharacteristics function and the ignition timing setting function, andthe charging efficiency corresponding to the target torque is calculatedusing the approximated curve, therefore the calculation using the torquecharacteristics function and the ignition timing setting function can bereduced to the preliminarily set intake sample numbers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram of an internal combustionengine and a controller according to Embodiment 1;

FIG. 2 is a schematic block diagram of a controller according toEmbodiment 1;

FIG. 3 is a hardware configuration diagram of a controller according toEmbodiment 1;

FIG. 4 is a figure showing an ignition timing setting functionconfigured by FNN according to Embodiment 1;

FIG. 5 is a figure showing a torque characteristics function configuredby FNN according to Embodiment 1;

FIG. 6 is a block diagram for explaining calculation processing of atarget ignition timing according to Embodiment 1;

FIG. 7 is a figure for explaining an ignition torque approximated curveaccording to Embodiment 1;

FIG. 8 is a block diagram for explaining calculation processing of atarget charging efficiency according to Embodiment 1;

FIG. 9 is a figure for explaining an intake torque approximated curveaccording to Embodiment 1;

FIG. 10 is a block diagram for explaining processing of a combustioncontrol target calculation unit and a combustion control unit accordingto Embodiment 1; and

FIG. 11 is a flowchart for explaining calculation processing of targetignition timing and target charging efficiency according to Embodiment1.

DETAILED DESCRIPTION OF THE EMBODIMENTS Embodiment 1

A controller 30 for an internal combustion engine (hereinafter, referredto simply as the controller 30) according to Embodiment 1 will beexplained with reference to the drawings. FIG. 1 is a schematicconfiguration diagram of the internal combustion engine 1, and FIG. 2 isa block diagram of the controller 30 according to Embodiment 1. Theinternal combustion engine 1 and the controller 30 are mounted in avehicle; the internal combustion engine 1 functions as a driving-forcesource for the vehicle (wheels).

1. Configuration of Internal Combustion Engine 1

As shown in FIG. 1, the internal combustion engine 1 is provided with acombustion chamber 25 in which a fuel-air mixture is combusted. Theinternal combustion engine 1 is provided with an intake pipe 23 forsupplying air to the combustion chamber 25 and an exhaust pipe 17 fordischarging exhaust gas from the combustion chamber 25. The combustionchamber 25 is configured by a cylinder and a piston. Hereinafter, thecombustion chamber 25 is also referred to the cylinder. The internalcombustion engine 1 is a gasoline engine. The internal combustion engine1 has a throttle valve 6 for opening and closing the intake pipe 23. Thethrottle valve 6 is an electronically controlled throttle valve which isopening/closing-driven by an electric motor controlled by the controller30. The throttle valve 6 is provided with a throttle opening degreesensor 7 which generates an electric signal according to a throttleopening degree of the throttle valve 6.

In the intake pipe 23 at the upstream side of the throttle valve 6,there are provided an air flow sensor 3 which outputs an electric signalaccording to an intake air flow rate taken into the intake pipe 23, andan intake air temperature sensor 4 which outputs an electric signalaccording to a temperature of intake air. The temperature of intake airdetected by the intake air temperature sensor 4 can be regarded as equalto an outside air temperature.

The internal combustion engine 1 has an EGR passage 21 whichrecirculates exhaust gas from the exhaust pipe 17 to the intake manifold12, and an EGR valve 22 which opens and closes the EGR passage 21. Theintake manifold 12 is a part of the intake pipe 23 at the downstreamside of the throttle valve 6. The EGR valve 22 is an electroniccontrolled EGR valve which is opening/closing-driven by an electricmotor controlled by controller 30. The EGR valve 22 is provided with anEGR opening degree sensor 27 which outputs an electric signal accordingto the opening degree of the EGR valve 22. “EGR” is an acronym forExhaust Gas Recirculation. EGR that the exhaust gas recirculates via theEGR valve 22 is called as external EGR, and EGR that the exhaust gasremains in the combustion chamber by valve overlap of intake and exhaustvalves is called as internal EGR. Hereinafter, external EGR is simplycalled as EGR.

In the intake manifold 12, there are provided a manifold pressure sensor8 which outputs an electric signal according to a manifold pressure,which is a pressure of gas in the intake manifold 12, and a manifoldtemperature sensor 9 which outputs an electric signal according to amanifold temperature, which is a temperature of gas in the intakemanifold 12.

The internal combustion engine 1 is provided with an injector 13 whichsupplies fuel to the combustion chamber 25. The injector 13 is providedin such a way as to inject a fuel directly into the combustion chamber25. The injector 13 may be provided so as to inject fuel to a downstreamside part of the intake manifold 12. The internal combustion engine 1 isprovided with an atmospheric pressure sensor 2 which outputs an electricsignal according to an atmospheric pressure.

An ignition plug for igniting a fuel-air mixture and an ignition coil 16for supplying ignition energy to the ignition plug are provided on thetop of the combustion chamber 25. On the top of the combustion chamber25, there are provided an intake valve 14 for adjusting an intake airamount to be taken from the intake pipe 23 into the combustion chamber25 and an exhaust valve 15 for adjusting an exhaust gas amount to beexhausted the combustion chamber 25 to the exhaust pipe 17. The intakevalve 14 is provided with an intake variable valve timing mechanismwhich makes the opening and closing timing thereof variable. The exhaustvalve 15 is provided with an exhaust variable valve timing mechanismwhich makes the opening and closing timing thereof variable. Each of thevariable valve timing mechanisms 14, 15 has an electric actuator. On thecrankshaft of the internal combustion engine 1, there is provided acrank angle sensor 20 for generating an electric signal according to therotation angle thereof. A knock sensor 28 is fixed to the cylinderblock.

In the exhaust pipe 17, there is provided an air-fuel ratio sensor 18which generates an electric signal according to an air-fuel ratio AF,which is the ratio of air to fuel in exhaust gas. A catalyst 19 forpurifying exhaust gas is also provided in the exhaust pipe 17.

2. Configuration of Controller 30

Next, the controller 30 will be explained. The controller 30 is acontroller whose control subject is the internal combustion engine 1. Asshown in the block diagram of FIG. 2, the controller 30 is provided withcontrol units such as a torque control unit 31, a torque interface unit32, and an engine control unit 33. The respective control units 31 to 33and the like of the controller 30 are realized by processing circuitsincluded in the controller 30. Specifically, as shown in FIG. 2, thecontroller 30 includes, as processing circuits, an arithmetic processor(computer) 90 such as a CPU (Central Processing Unit), storageapparatuses 91 which exchange data with the arithmetic processor 90, aninput circuit 92 which inputs external signals to the arithmeticprocessor 90, an output circuit 93 which outputs signals from thearithmetic processor 90 to the outside, a communication circuit 94, andthe like.

As the arithmetic processor 90, ASIC (Application Specific IntegratedCircuit), IC (Integrated Circuit), DSP (Digital Signal Processor), FPGA(Field Programmable Gate Array), various kinds of logical circuits,various kinds of signal processing circuits, and the like may beprovided. As the arithmetic processor 90, a plurality of the same typeones or the different type ones may be provided, and each processing maybe shared and executed. As the storage apparatuses 91, there areprovided a RAM (Random Access Memory) which can read data and write datafrom the arithmetic processor 90, a ROM (Read Only Memory) which canread data from the arithmetic processor 90, and the like. The inputcircuit 92 is connected with various kinds of sensors and switches andis provided with an A/D converter and the like for inputting outputsignals from the sensors and the switches to the arithmetic processor90. The output circuit 93 is connected with electric loads and isprovided with a driving circuit and the like for outputting a controlsignal from the arithmetic processor 90.

The communication circuit 94 is connected with external controllers,such as a transmission controller 95 which controls a transmission, amotor controller 96 which controls a motor provided in the hybridvehicle, and a brake traction controller 97 which performs brake controland traction control, through a communication wire, and performs cablecommunication based on a communication protocol such as the CAN(Controller Area Network).

Then, the arithmetic processor 90 runs software items (programs) storedin the storage apparatus 91 such as a ROM and collaborates with otherhardware devices in the controller 30, such as the storage apparatus 91,the input circuit 92, and the output circuit 93, so that the respectivefunctions of the control units 31 to 33 included in the controller 50are realized. Setting data items such as each function and constants tobe utilized in the control units 31 to 33 are stored, as part ofsoftware items (programs), in the storage apparatus 91 such as a ROM.

In the present embodiment, the input circuit 92 is connected with theatmospheric pressure sensor 2, the air flow sensor 3, the intake airtemperature sensor 4, the throttle position sensor 7, the manifoldpressure sensor 8, the manifold temperature sensor 9, the air-fuel ratiosensor 18, the crank angle sensor 20, the accelerator opening degreesensor 26, the EGR opening degree sensor 27, the knock sensor 28, andthe like. The output circuit 93 is connected with the throttle valve 6(electric motor), the injector 13, the intake variable valve timingmechanism 14, the exhaust variable valve timing mechanism 15, theignition coil 16, the EGR valve 22 (the electric actuator), and thelike. The controller 30 is connected with various kinds of unillustratedsensors, switches, actuators, and the like.

2-1. Torque Base Control

The controller 30 performs torque base control that controls theinternal combustion engine 1 based on a target torque. The controller 30is provided with the torque control unit 31, the torque interface unit32, and the engine control unit 33 schematically, as mentioned above.The torque control unit 31 calculates the target torque. The torqueinterface unit 32 calculates target values of controlled variables ofthe internal combustion engine based on the target torque. The enginecontrol unit 33 performs driving control of various kinds of electricloads based on the target values of controlled variables.

<Torque Control Unit 31>

The torque control unit 31 calculates a driver request torque which isan output torque that a driver requires on the internal combustionengine 1, based on the actual accelerator opening degree detected by theaccelerator opening degree sensor 26. The torque control unit 31calculates an idling torque which is an output torque necessary formaintaining rotational speed at idling operation. The torque controlunit 31 calculates an external request torque which is an output torquerequired from the external controllers such as the transmissioncontroller 95, the motor controller 96, and the brake tractioncontroller 97. Then, the torque control unit 31 calculates the targettorque by determining the priority among the driver request torque, theidling torque, and the external request torque (such calculation is alsocalled as torque adjustment).

Here, the target torque contains a low response target torque Trqts anda high response target torque Trqtf. The low response target torqueTrqts is an output torque required for the internal combustion enginewithout considering retarding the ignition timing; and the high responsetarget torque Trqtf is an output torque required for the internalcombustion engine including retarding the ignition timing. Normally,although the low response target torque Trqts and the high responsetarget torque Trqtf coincide with each other, when there is a torquedown request by retarding ignition timing, the high response targettorque Trqtf becomes lower than the low response target torque Trqts.

The torque control unit 31 mainly calculates the low response targettorque Trqts based on the larger one of the driver request torque andthe idling torque in a steady state, and calculates the high responsetarget torque Trqtf based on the external request torque and the idlingtorque at load change.

<Torque Interface Unit 32>

The torque interface unit 32 performs interconversion between the targettorque and the charging efficiency, and interconversion between thetarget torque and the ignition timing, based on the driving conditionsof the internal combustion engine; and calculates a target chargingefficiency Ect and a target ignition timing IGt to transmit to theengine control unit 33. The torque interface unit 32 calculates anactual output torque Trqr based on the driving conditions of theinternal combustion engine to transmit to the torque control unit 31.Detailed processing of the torque interface unit 32 is described below.

<Driving Condition Detection Unit 330>

The engine control unit 33 is provided with a driving conditiondetection unit 330 that detects the driving conditions of the internalcombustion engine. The driving condition detection unit 330 detectsvarious kinds of driving conditions, based on the output signals ofvarious kinds of sensors and the like. Specifically, the drivingcondition detection unit 330 detects actual an atmospheric pressurebased on the output signal of the atmospheric pressure sensor 2; detectsan actual intake air flow rate based on the output signal of the airflow sensor 3; detects an actual outside air temperature based on theoutput signal of the intake air temperature sensor 4; detects an actualthrottle opening degree based on the output signal of the throttleposition sensor 7; detects an actual manifold pressure based on theoutput signal of the manifold pressure sensor 8; detects an actualmanifold temperature which is a temperature of gas in the intakemanifold 12 based on the output signal of the manifold temperaturesensor 9 and the like; detects an actual air fuel ratio of exhaust gasbased on the output signal of the air-fuel ratio sensor 18; detects anactual accelerator opening degree based on the output signal of theaccelerator opening degree sensor 26; and detects an actual EGR openingdegree based on the output signal of an EGR opening degree sensor 27.

The driving condition detection unit 330 detects a crank angle and anactual rotational speed Ner based on the output signal of the crankangle sensor 20. The driving condition detection unit 330 detects anactual phase angle IVTr of the intake variable valve timing mechanism 14(hereinafter, referred to as the intake VVT 14) and an actual phaseangle EVTr of the exhaust gas variable valve timing mechanism 15(hereinafter, referred to as the exhaust VVT 15), based on a phasedifference between edge of a cam angle sensor (unillustrated) and thecrank angle 8 d.

The driving condition detection unit 330 detects an in-cylinder intakeair amount information which is information of an air amount taken intothe combustion chamber 25. The driving condition detection unit 330calculates an actual intake air amount [g/stroke] taken into thecombustion chamber 25 and an actual charging efficiency Ecr [%] as thein-cylinder intake air amount information, based on the actual intakeair flow rate, the actual rotational speed Ner, and the like. Forexample, the driving condition detection unit 330 calculates, as theactual intake air amount [g/stroke], a value obtained by applying filterprocessing which simulates a delay in the intake manifold to a valueobtained by multiplying a stroke period according to the rotationalspeed Ne to the actual intake air flow rate [g/s]. Alternatively, thedriving condition detection unit 330 may calculate the actual intake airamount [g/stroke] and the actual charging efficiency Ecr [%], based onthe actual manifold pressure, the actual rotational speed Ner, and thelike.

The driving condition detection unit 330 calculates an actual EGR amount[g/stroke] which is an actual exhaust gas recirculation amount takeninto the combustion chamber 25, based on the EGR opening degree and thelike. For example, the driving condition detection unit 330 calculatesan actual EGR flow rate [g/s] which passes the EGR valve 22, based onthe EGR opening degree, the manifold pressure, and the like; andcalculates, as the actual EGR amount [g/stroke], a value obtained byapplying filter processing to a value obtained by multiplying the strokeperiod to the actual EGR flow rate. The driving condition detection unit330 calculates an actual EGR rate Regrr [%] which is a ratio of theactual EGR amount to the actual intake air amount.

<Intake Air Amount Control Unit 331>

The engine control unit 33 is provided with an intake air amount controlunit 331 that controls intake air amount. The intake air amount controlunit 331 calculates a target intake air amount from the target chargingefficiency Ect, and calculates a target intake air flow rate from thetarget intake air amount. The engine control unit 33 calculates a targetthrottle opening degree based on the actual intake air flow rate and theactual manifold pressure so as to achieve the target intake air flowrate, and performs driving control of the electric motor of the throttlevalve 6.

<Combustion Control Unit 334>

The engine control unit 33 is provided with a combustion control unit334 that controls combustion operation mechanism for operatingcombustion state. In the present embodiment, the combustion operationmechanism is set to the EGR valve 22, the intake VVT 14, and the exhaustVVT 15. The combustion control unit 334 performs driving control of eachcombustion operation mechanism based on the target value of eachcombustion control state transmitted from the combustion control targetcalculation unit 66 described below, as shown in FIG. 10. The combustioncontrol unit 334 calculates a target EGR opening degree so as to achievethe target EGR rate Regrt, and performs driving control of the electricactuator of the EGR valve 22. The combustion control unit 334 performsdriving control of the electric actuator of the intake VVT 14 so as toachieve the target phase angle IVTt of the intake VVT 14 (hereinafter,referred to as the target intake phase angle IVTt). The combustioncontrol unit 334 performs driving control of the electric actuator ofthe exhaust VVT 15 so as to achieve the target phase angle EVTt of theexhaust VVT 15 (hereinafter, referred to as the target exhaust phaseangle EVTt.

<Fuel Control Unit 332>

The engine control unit 33 is provided with a fuel control unit 332 thatcontrols fuel injection amount. The fuel control unit 332 calculates afuel injection amount for achieving a target air fuel ratio based on theactual charging efficiency Ecr, and performs driving control of theinjector 13.

<Ignition Control Unit 333>

The engine control unit 33 is provided with an ignition control unit 333that performs energization to the ignition coil. The ignition controlunit 333 determines a final ignition timing SA based on the targetignition timing IGt transmitted from the torque interface unit 32. Whenknock is detected by the knock sensor 28, the ignition control unit 333calculates the final ignition timing SA by performing retard anglecorrection to the target ignition timing IGt so as not to cause knock.The ignition control unit 333 performs retard angle limitation thatlimits the ignition timing of retard side by a retard limit ignitiontiming IGrtd so that the final ignition timing SA is not set to retardside rather than the retard limit ignition timing IGrtd for preventingmisfire. Then, the ignition control unit 333 performs energizationcontrol to the ignition coil 16 based on the final ignition timing SA.This final ignition timing SA becomes an actual ignition timing SA.

2-2. Detailed Configuration of Torque Interface Unit 32

As mentioned above, the torque interface unit 32 performsinterconversion between the target torque and the charging efficiency,and interconversion between the target torque and the ignition timing,based on the driving conditions of the internal combustion engine, andcalculates a target charging efficiency Ect and a target ignition timingIGt. For that purpose, a torque characteristics function and an ignitiontiming setting function which are explained below are stored in thestorage apparatus 91.

2-2-1. Ignition Timing Setting Function

The torque interface unit 32 stores the ignition timing setting functionin which a relationship between preliminarily set kinds of drivingconditions and a basic value of target ignition timing IGb ispreliminarily set. In a driving condition where knock does not occur ata MBT ignition timing IGmbt (MBT: Minimum advance for the Best Torque)which is an ignition timing when the output torque becomes the maximum,the basic value of target ignition timing IGb is set to the MBT ignitiontiming IGmbt; and in a driving condition where knock occurs at the MBTignition timing IGmbt, the basic value of target ignition timing IGb isset to a knock limit ignition timing IGknk which is a limit ignitiontiming of advance side when knock starts to occur.

The ignition timing setting function is a function in which arelationship between preliminarily set kinds of driving conditionsincluding the charging efficiency Ec and the basic value of targetignition timing IGb is preliminarily set. The driving conditions whichinfluence on the ignition timing when the output torque becomes themaximum change on the system structure of the internal combustion engine1. In the present embodiment, the ignition timing setting function is afunction in which a relationship between driving conditions of therotational speed Ne, the charging efficiency Ec, the intake phase angleIVT, the exhaust phase angle EVT, and the EGR rate Regr, and the basicvalue of target ignition timing IGb is preliminarily set.

<Neural Network>

When the system structure of the internal combustion engine 1 becomescomplex, the ignition timing setting function becomes a complex functionwith many input variables. In the present embodiment, as shown in FIG.4, the ignition timing setting function is configured by a feedforwardpropagation type neural network (FNN: Feedforward Neural Network). FNNhas a structure in which units (also called as node, neuron) arranged ina hierarchical manner are connected between adjoining layers, and is anetwork configured so that information propagates from input side towardoutput side. In the calculation performed in the unit, weights areapplied and biases are added to values inputted from respective units ina former layer, and then these become a total input to this unit; andthis total input is inputted into an activation function, and its outputbecomes an output of the unit.

In order to use FNN configured by such units as approximation function,it is necessary to adjust the weights and the biases of each unit sothat the input values to FNN and its output value become desiredrelationship. Many data sets of the input values and the output valuewhich are called teacher data are previously prepared for thisadjustment, and it is performed by applying a method called error backpropagation method (back-propagation method). To adjust weights andbiases in this way is called as learning of neural network; and whenlearning is performed well, FNN can be used as a general-purposefunction which memorized the feature of teacher data.

Although it is considered that approximate precision is improved, as thenumber of layers of FNN becomes larger and the number of units includedin a layer becomes larger; accuracy may be extremely deteriorated indifferent points from teacher data depending on the condition oflearning (this is called as over learning or excess adaptation); in sucha case, it is necessary to adjust so as to obtain necessary approximateprecision by stopping learning on the way to suppress over learning, andby increasing the number of teacher data. Although the above is anoutline of FNN, since FNN and its learning method are well-knowntechnology as explained in “Machine learning professional series deeplearning”, Takayuki Okaya, Kodansha, 2015, above-mentioned FNN isexplained as well-known.

In an example shown in FIG. 4, as the configuration of FNN, fiveparameters of the rotational speed Ne, the charging efficiency Ec, theintake phase angle IVT, the exhaust phase angle EVT, and the EGR rateRegr are inputted into the input layer; there are three middle layers ofwhich has five units; and the basic value of target ignition timing IGbis outputted from the output layer. This configuration is exemplary, itmay be configured so that environmental conditions, such as theintake-air temperature, the atmospheric pressure, and the manifoldtemperature, are inputted, and it may be configured so that the otherdriving conditions of the internal combustion engines such as theair-fuel ratio AF are inputted. If the system structure of the internalcombustion engine is different, it may be configured so that the drivingconditions of its system structure (for example, a variable valve lift,a variable compression ratio, and the like) are inputted. Also aboutmiddle layers, the number of units of each layer and the number oflayers itself may be increased or decreased. These are the parameterswhich should be adjusted depending on approximate precision at learningof FNN performed beforehand.

Here, the example in which the basic value of target ignition timing IGbis directly calculated by one FNN is shown. However, two FNN of FNN forcalculation of the MBT ignition timing IGmbt and FNN for calculation ofthe knock limit ignition timing IGknk may be provided; the MBT ignitiontiming IGmbt and the knock limit ignition timing IGknk are calculated byeach FNN; and the ignition timing at the retard side out of these twoignition timings may be calculated as the basic value of target ignitiontiming IGb.

2-2-2. Torque Characteristics Function

The torque interface unit 32 stores the torque characteristics functionin which a relationship between preliminarily set kinds of drivingconditions and the output torque Trq is preliminarily set. Then, thetorque interface unit 32 calculates the target values of controlledvariables which realize the target torque, by using the torquecharacteristics function.

The torque characteristics function is a function in which arelationship between preliminarily set kinds of driving conditionsincluding ignition timing IG and the output torque Trq is preliminarilyset. The driving conditions which influence on the output torque changedepending on the system structure of the internal combustion engine 1.In the present embodiment, the torque characteristics function is afunction in which a relationship between driving conditions of therotational speed Ne, the charging efficiency Ec, the intake phase angleIVT, the exhaust phase angle EVT, the EGR rate Regr, and the ignitiontiming IG, and the output torque Trq is preliminarily set.

When the system structure of the internal combustion engine 1 becomescomplex, the torque characteristics function becomes a complex with manyinput variables. In the present embodiment, as shown in FIG. 5, thetorque characteristics function is configured by the feedforwardpropagation type neural network (FNN).

In an example shown in FIG. 5, as the configuration of FNN, sixparameters of the rotational speed Ne, the charging efficiency Ec, theintake phase angle IVT, the exhaust phase angle EVT, the EGR rate Regr,and the ignition timing IG are inputted into the input layer; there arethree middle layers each of which has six units; and the output torqueTrq is outputted from the output layer.

This configuration is exemplary, it may be configured so thatenvironmental conditions, such as the intake-air temperature, theatmospheric pressure, and the manifold temperature, are inputted, and itmay be configured so that the other driving conditions of the internalcombustion engines such as the air-fuel ratio AF are inputted. If thesystem structure of the internal combustion engine is different, it maybe configured so that the driving conditions of its system structure(for example, a variable valve lift, a variable compression ratio, andthe like) are inputted. Also about middle layers, the number of units ofeach layer and the number of layers itself may be increased ordecreased. These are the parameters which should be adjusted dependingon approximate precision at learning of FNN performed beforehand.

Here, the example in which the output torque Trq is directly calculatedby FNN is shown. However, an indicated mean effective pressure or athermal efficiency may be calculated by FNN; and the output torque Trqmay be calculated by multiplying a stroke volume and the like to theindicated mean effective pressure, or the output torque Trq may becalculated by multiplying a heat amount of fuel and the like to thethermal efficiency.

2-2-3. Calculation of Actual Output Torque Trqr

The torque interface unit 32 is provided with an actual torquecalculation unit 55 that calculates an actual output torque Trqr. Theactual torque calculation unit 55 calculates the actual output torqueTrqr which is the output torque corresponding to the present drivingconditions (in this example, the actual rotational speed Ner, the actualcharging efficiency Ecr, the actual intake phase angle IVTr, the actualexhaust phase angle EVTr, the actual EGR rate Regrr, and the actualignition timing SA), by using the torque characteristics function. Thecalculated actual output torque Trqr is transmitted to the torquecontrol unit 31.

2-2-4. Calculation of Target Ignition Timing IGt

The torque interface unit 32 is provided with a target ignition timingcalculation unit 51 that calculates a target ignition timing IGt. In thepresent embodiment, as shown in a next equation and FIG. 6, when thehigh response target torque Trqtf coincides with the low response targettorque Trqts and there is no torque down request by retarding ignitiontiming, the target ignition timing calculation unit 51 calculates thebasic value of target ignition timing IGb corresponding to the presentdriving conditions, as the target ignition timing IGt; and when the highresponse target torque Trqtf is lower than the low response targettorque Trqts and there is a torque down request by retarding ignitiontiming, the target ignition calculation unit 51 calculates a targettorque corresponding ignition timing IGtt corresponding to the highresponse target torque Trqtf, as the target ignition timing IGt.

When Trqtf=Trqts  1)

IGt=IGb

When Trqtf<Trqts  2)

IGt=IGtt  (1)

2-2-4-1. Calculation of Basic Value of Target Ignition Timing IGb

The target ignition timing calculation unit 51 calculates the basicvalue of target ignition timing IGb corresponding to the drivingconditions (in this example, the actual rotational speed Ner, the actualcharging efficiency Ecr, the actual intake phase angle IVTr, the actualexhaust phase angle EVTr, and the actual EGR rate Regrr), by using theignition timing setting function.

2-2-4-2. Calculation of Target Torque Corresponding Ignition Timing

The target ignition timing calculation unit 51 calculates the targettorque corresponding ignition timing IGtt which realizes the targettorque. In the present embodiment, the target ignition timingcalculation unit 51 calculates the target torque corresponding ignitiontiming IGtt which realize the high response target torque Trqtf which isthe output torque required for the internal combustion engine includingretarding ignition timing.

If the ignition timing IG is changed little by little and the outputtorque Trq is calculated repeatedly using the torque characteristicsfunction, the ignition timing IG which realizes the high response targettorque Trqtf can be searched. However, if the calculation using thetorque characteristics function is performed repeatedly, arithmetic loadis increased. Especially, if system structure becomes complex and thetorque characteristics function becomes complex, arithmetic load isincreased significantly. Therefore, it is desired to lower the number ofcalculations using the torque characteristics function as much aspossible.

Then, as shown in FIG. 6, the target ignition timing calculation unit 51is provided with a plural ignition torque calculation unit 52, anignition torque approximated curve calculation unit 53, and anapproximated curve ignition calculation unit 54. The plural ignitiontorque calculation unit 52 calculates ignition sample numbers ofignition corresponding torques Trqi1, Trqi2 . . . which are the ignitionsample numbers of output torques corresponding to the respectiveignition sample numbers of ignition timings IG1, IG2 . . . which arepreliminarily set to plural numbers, by using the torque characteristicsfunction.

The ignition torque approximated curve calculation unit 53 calculates anignition torque approximated curve which is an approximated curveapproximating a relationship between the ignition sample numbers of theignition timings IG1, IG2 . . . and the ignition sample numbers of theignition corresponding torques Trqi1, Trqi2 . . . . The approximatedcurve ignition calculation unit 54 calculates the ignition timingcorresponding to the target torque (in this example, the high responsetarget torque Trqtf), as the target torque corresponding ignition timingIGtt, by using the ignition torque approximated curve.

According to this configuration, without performing the calculationusing the torque characteristics function repeatedly to search theignition timing corresponding to the target torque directly, theapproximated curve is calculated based on the ignition sample numbers ofcalculation results of the torque characteristics function, and theignition timing corresponding to the target torque is calculated usingthe approximated curve, therefore the calculation using the torquecharacteristics function can be reduced to the preliminarily setignition sample numbers.

<Setting of Three Ignition Sample Numbers of Ignition Timings>

In the present embodiment, a case where the ignition sample numbers isset to three will be explained. That is to say, the calculation usingthe torque characteristics function is performed for each of the firstsample of ignition timing IG1, the second sample of ignition timing IG2,and the third sample of ignition timing IG3, and the first sample ofignition corresponding torque Trqi1, the second sample of ignitioncorresponding torque Trqi2, and the third sample of ignitioncorresponding torque Trqi3 are calculated.

The plural ignition torque calculation unit 52 sets the first sample ofignition timing IG1, the second sample of ignition timing IG2, and thethird sample of ignition timing IG3, to mutually different values withina combustible range. For example, as shown in a next equation, theplural ignition torque calculation unit 52 sets the first sample ofignition timing IG1 to the basic value of target ignition timing IGb,sets the third sample of ignition timing IG3 to the retard limitignition timing IGrtd which is a setting limit of the ignition timing onthe retard side, and sets the second sample of ignition timing IG2 to anintermediate value between the basic value of target ignition timing IGband the retard limit ignition timing IGrtd.

$\begin{matrix}{{{{IG}\; 1} = {IGb}},\; {{{IG}\; 3} = {IGrtd}},\mspace{11mu} {{{IG}\; 2} = \frac{{IGb} + {IGrtd}}{2}}} & (2)\end{matrix}$

<Calculation of Three Ignition Sample Numbers of Ignition CorrespondingTorques>

The plural ignition torque calculation unit 52 calculates the firstsample of ignition corresponding torque Trqi1 which is the output torquecorresponding to the actual rotational speed Ner, the actual chargingefficiency Ecr, the actual intake phase angle IVTr, the actual exhaustphase angle EVTr, the actual EGR rate Regrr, and the first sample ofignition timing IG1, by using the torque characteristics function. Next,the plural ignition torque calculation unit 52 calculates the secondsample of ignition corresponding torque Trqi2 which is the output torquecorresponding to the actual rotational speed Ner, the actual chargingefficiency Ecr, the actual intake phase angle IVTr, the actual exhaustphase angle EVTr, the actual EGR rate Regrr, and the second sample ofignition timing IG2, by using the torque characteristics function. Then,the plural ignition torque calculation unit 52 calculates the thirdsample of ignition corresponding torque Trqi3 which is the output torquecorresponding to the actual rotational speed Ner, the actual chargingefficiency Ecr, the actual intake phase angle IVTr, the actual exhaustphase angle EVTr, the actual EGR rate Regrr, and the third sample ofignition timing IG3, by using the torque characteristics function.

<Calculation of Ignition Torque Approximated Curve>

The relationship between the first sample to the third sample ofignition timings IG1, IG2, IG3, and the first sample to the third sampleof ignition corresponding torques Trqi1, Trqi2, Trqi3 is shown in FIG.7. Generally, if the driving conditions other than the ignition timingare the same, it is considered that the relationship between theignition timing and the torque can be approximated by a quadraticfunction (see the paragraph 0032 and the like of JP 4499809 B).

Then, in the present embodiment, the ignition torque approximated curveis set to a quadratic function as shown in a next equation. The ignitiontorque approximated curve calculation unit 53 calculates coefficients A,B, C of respective terms of the ignition torque approximated curve whichis set to the quadratic function, based on the ignition sample numbersof the ignition timings IG1, IG2 . . . and the ignition sample numbersof the ignition corresponding torques Trqi1, Trqi2 . . . .

Trq=A×IG ² +B×IG+C  (3)

In this quadratic function, if there are three points of relationshipbetween the ignition timing IG and the output torque Trq, the threecoefficients A, B, C can be calculated by substituting these to theequation (3) respectively and solving simultaneous equations. Forexample, the ignition torque approximated curve calculation unit 53calculates the three coefficients A, B, C using a next equation.

$\begin{matrix}{\begin{bmatrix}A \\B \\C\end{bmatrix} = {\begin{bmatrix}{{IG}\; 1^{2}} & {{IG}\; 1} & 1 \\{{IG}\; 2^{2}} & {{IG}\; 2} & 1 \\{{IG}\; 3^{2}} & {{IG}\; 3} & 1\end{bmatrix}^{- 1}\begin{bmatrix}{{Trqi}\; 1} \\{{Trqi}\; 2} \\{{Trqi}\; 3}\end{bmatrix}}} & (4)\end{matrix}$

The ignition sample numbers may be preliminarily set to four or morenumbers, four or more points of the relationship between the ignitiontiming IG and the output torque Trq are calculated, and by a method ofregression analysis such as the least square method, the coefficients A,B, C of respective terms may be calculated.

<If Ignition Sample Numbers are Two>

Alternatively, the ignition sample numbers may be preliminarily set totwo. In this case, as shown in a next equation, the ignition torqueapproximated curve calculation unit 53 sets the first sample of ignitiontiming IG1 to the MBT ignition timing IGmbt which is the ignition timingwhen the output torque becomes the maximum, and sets the second sampleof ignition timing IG2 to the retard limit ignition timing IGrtd whichis the setting limit of the ignition timing on the retard side.Similarly to the ignition timing setting function, the MBT ignitiontiming IGmbt is calculated using a function in which a relationshipbetween preliminarily set kinds of driving conditions and the MBTignition timing IGmbt is preliminarily set; and the function isconfigured by a neural network. Alternatively, as mentioned above, iftwo FNN of FNN for calculation of the MBT ignition timing IGmbt and FNNfor calculation of the knock limit ignition timing IGknk are provided asthe ignition timing setting function, the MBT ignition timing IGmbtcalculated when calculating the basic value of target ignition timingIGb may be used.

IG1=IGmbt,IG2=IGrtd  (5)

The plural ignition torque calculation unit 52 calculates the firstsample of ignition corresponding torque Trqi1 corresponding to the MBTignition timing IGmbt, by using the torque characteristics function, andcalculates the second sample of ignition corresponding torque Trqi2corresponding to the retard limit ignition timing IGrtd, by using atorque characteristics function.

Then, as shown in a next equation, the ignition torque approximatedcurve calculation unit 53 sets the first sample of ignitioncorresponding torque Trqi1 corresponding to the MBT ignition timingIGmbt, and the MBT ignition timing IGmbt, to extremums of the ignitiontorque approximated curve which is set to a the quadratic function.

$\begin{matrix}{{Trq} = {{A \times \left( {{IG} + \frac{B}{2A}} \right)^{2}} + C - \frac{B^{2}}{4A}}} & (6) \\{{\frac{B}{2A} = {- {IGmbt}}},\mspace{14mu} {{C - \frac{B^{2}}{4A}} = {{Trqi}\; 1}}} & \;\end{matrix}$

Then, as shown in a next equation, the ignition torque approximatedcurve calculation unit 53 calculates the coefficients A, B, C ofrespective terms of the ignition torque approximated curve, based on thesecond sample of ignition corresponding torque Trqi2 corresponding tothe retard limit ignition timing IGrtd, and the retard limit ignitiontiming IGrtd.

$\begin{matrix}{{{Trqi}\; 2} = {{A \times \left( {{IGrtd} - {IGmbt}} \right)^{2}} + {{Trqi}\; 1}}} & (7) \\{A = \frac{{{Trqi}\; 2} - {{Trqi}\; 1}}{\left( {{IGrtd} - {IGmbt}} \right)^{2}}} & \; \\{B = {{- {IGmbt}} \times 2A}} & \; \\{C = {{{Trqi}\; 1} + \frac{B^{2}}{4A}}} & \;\end{matrix}$

<Calculation of Target Torque Corresponding Ignition Timing UsingIgnition Torque Approximated Curve>

As shown in a next equation, the approximated curve ignition calculationunit 54 calculates the ignition timing corresponding to the highresponse target torque Trqtf by solving the equation of the quadraticfunction and using the coefficient A, B, C, as the target torquecorresponding ignition timing IGtt.

$\begin{matrix}{{{A \times {IGtt}^{2}} + {B \times {IGtt}} + \left( {C - {Trqtf}} \right)} = 0} & (8) \\{{IGtt} = \frac{{- B} + \sqrt{B^{2} - {4 \times A \times \left( {C - {Trqtf}} \right)}}}{2 \times A}} & \;\end{matrix}$

2-2-5. Calculation of Target Charging Efficiency Ect

The torque interface unit 32 is provided with a target intake air amountcalculation unit 61 that calculates the target charging efficiency Ect.The target intake air amount calculation unit 61 calculates the targetcharging efficiency Ect which realizes the target torque. In the presentembodiment, the target intake air amount calculation unit 61 calculatesthe target charging efficiency Ect which realizes the low responsetarget torque Trqts which is the output torque required for the internalcombustion engine without considering retarding the ignition timing.

If the charging efficiency Ec is changed little by little and the outputtorque Trq is calculated repeatedly using the torque characteristicsfunction, the charging efficiency Ec which realizes the low responsetarget torque Trqt can be searched. In this case, since the basic valueof target ignition timing IGb is also changed when the chargingefficiency Ec is changed, it is necessary to also calculate the basicvalue of target ignition timing IGb using the ignition timing settingfunction every time when the charging efficiency Ec is changed. However,if the calculation using the torque characteristics function and thecalculation using the ignition timing setting function are performedrepeatedly, arithmetic load is increased. Especially, if systemstructure becomes complex, and the torque characteristics function andthe ignition timing setting function become complex, arithmetic load isincreased significantly. Therefore, it is desired to lower the number ofcalculations using the torque characteristics function and the ignitiontiming setting function as much as possible.

Then, as shown in FIG. 8, the target intake air amount calculation unit61 is provided with a plural intake ignition calculation unit 62, aplural intake torque calculation unit 63, an intake torque approximatedcurve calculation unit 64, and a torque intake air amount calculationunit 65. The plural intake ignition calculation unit 62 calculatesintake sample numbers of the basic values of target ignition timingIGb1, IGb2 . . . corresponding to the respective intake sample numbersof the charging efficiencies Ec1, Ec2 . . . which are preliminarily setto plural numbers, by using the ignition timing setting function.

The plural intake torque calculation unit 63 calculates the intakesample numbers of the intake ignition corresponding torques Trqe1, Trqe2. . . which are the intake sample numbers of the output torquescorresponding to the respective intake sample numbers of the chargingefficiencies Ec1, Ec2 . . . and the respective intake sample numbers ofthe basic values of target ignition timing IGb1, IGb2 . . . , by usingthe torque characteristics function.

The intake torque approximated curve calculation unit 64 calculates anintake torque approximated curve which is an approximated curveapproximating a relationship between the intake sample numbers of thecharging efficiencies Ec1, Ec2 . . . and the intake sample numbers ofthe intake ignition corresponding torques Trqe1, Trqe2 . . . . Thetorque intake air amount calculation unit 65 calculates the chargingefficiency corresponding to the target torque (in this example, the lowresponse target torque Trqts), as the target charging efficiency Ect, byusing the intake torque approximated curve.

According to this configuration, without performing the calculationusing the torque characteristics function and the ignition timingsetting function repeatedly to search the charging efficiencycorresponding to the target torque directly, the approximated curve iscalculated based on the intake sample numbers of calculation results ofthe torque characteristics function and the ignition timing settingfunction, and the charging efficiency corresponding to the target torqueis calculated using the approximated curve, therefore the calculationusing the torque characteristics function and the ignition timingsetting function can be reduced to the preliminarily set intake samplenumbers.

<Setting of Three Intake Sample Numbers of Charging Efficiencies>

In the present embodiment, a case where the intake sample numbers is setto three will be explained. As shown in a next equation, the pluralintake ignition calculation unit 62 sets the actual charging efficiencyEcr to the first sample of charging efficiency Ec1. The plural intakeignition calculation unit 62 calculates a value according to a valueobtained by multiplying a ratio of the low response target torque Trqtsto the actual output torque Trqr, to the actual charging efficiency Ecr,as a target corresponding charging efficiency, and sets it to the thirdsample of charging efficiency Ec3. The plural intake ignitioncalculation unit 62 calculates an intermediate value between the actualcharging efficiency Ecr (Ec1) and the target corresponding chargingefficiency (Ec3), as a middle charging efficiency, and sets it to thesecond sample of charging efficiency Ec2.

$\begin{matrix}{{{Ec}\; 1} = {Ecr}} & (9) \\{{{Ec}\; 3} = {{Ke} \times {Ecr} \times \frac{Trqts}{Trqr}}} & \; \\{{{Ec}\; 2} = \frac{{{Ec}\; 1} + {{Ec}\; 3}}{2}} & \;\end{matrix}$

Here, when “the actual output torque Trqr<the low response target torqueTrqts”, the adjustment factor Ke is set to a value about 1.2 to 1.5; andwhen “the actual output torque Trqr>the low response target torqueTrqts”, the adjustment factor Ke is set to a value about 0.7 to 0.9.

<Calculation of Target Values of Controlled Variables Other than ThreeIntake Sample Numbers of Ignition Timings>

If the charging efficiency Ec changes, not only the basic value oftarget ignition timing IGb but also the optimum values of othercontrolled variables of the internal combustion engines will change, andchange of the controlled variables will influence on the output torqueTrq. In the present embodiment, the plural intake ignition calculationunit 62 calculates target values of controlled variables of the internalcombustion engines other than the ignition timing (in this example, thetarget intake phase angle IVTt, the target exhaust phase angle EVTt, thetarget EGR rate Regrt) corresponding to the respective intake samplenumbers of the charging efficiencies Ec1, Ec2, Ec3, and uses these forthe calculation using the ignition timing setting function.

Specifically, the plural intake ignition calculation unit 62 calculatesthe intake sample numbers of the target intake phase angles IVTt1,IVTt2, IVTt3 corresponding to the actual rotational speed Ner and therespective intake sample numbers of the charging efficiencies Ec1, Ec2,Ec3, by using an intake phase angle target setting function describedbelow. The plural intake ignition calculation unit 62 calculates theintake sample numbers of the target exhaust phase angles EVTt1, EVTt2,EVTt3 corresponding to the actual rotational speed Ner and therespective intake sample numbers of the charging efficiencies Ec1, Ec2,Ec3, by using an exhaust phase angle target setting function describedbelow. The plural intake ignition calculation unit 62 calculates theintake sample numbers of the target EGR rates Regrt1, Regrt2, Regrt3corresponding to the actual rotational speed Ner and the respectiveintake sample numbers of the charging efficiencies Ec1, Ec2, Ec3, byusing an EGR rate target setting function described below.

<Calculation of Three Intake Sample Numbers of Basic Values of TargetIgnition Timing>

The plural intake ignition calculation unit 62 calculates the firstsample of the basic value of target ignition timing IGb1 correspondingto the actual rotational speed Ner, the first sample of the chargingefficiency Ec1, the first sample of the target intake phase angle IVTt1,the first sample of the target exhaust phase angle EVTt1, and the firstsample of the target EGR rate Regrt1, by using the ignition timingsetting function. Next, the plural intake ignition calculation unit 62calculates the second sample of the basic value of target ignitiontiming IGb2 corresponding to the actual rotational speed Ner, the secondsample of the charging efficiency Ec2, the second sample of the targetintake phase angle IVTt2, the second sample of the target exhaust phaseangle EVTt2, and the second sample of the target EGR rate Regrt2, byusing the ignition timing setting function. Then, the plural intakeignition calculation unit 62 calculates the third sample of the basicvalue of target ignition timing IGb3 corresponding to the actualrotational speed Ner, the third sample of the charging efficiency Ec3,the third sample of the target intake phase angle IVTt3, the thirdsample of the target exhaust phase angle EVTt3, and the third sample ofthe target EGR rate Regrt3, by using the ignition timing settingfunction.

<Calculation of Three Intake Sample Numbers of Intake IgnitionCorresponding Torques>

The plural intake torque calculation unit 63 calculates the first sampleof the intake ignition corresponding torque Trqe1 corresponding to theactual rotational speed Ner, the first sample of the charging efficiencyEc1, the first sample of the target intake phase angle IVTt1, the firstsample of the target exhaust phase angle EVTt1, the first sample of thetarget EGR rate Regrt1, and the first sample of the basic value oftarget ignition timing IGb1, by using the torque characteristicsfunction. Next, the plural intake torque calculation unit 63 calculatesthe second sample of the intake ignition corresponding torque Trqe2corresponding to the actual rotational speed Ner, the second sample ofthe charging efficiency Ec2, the second sample of the target intakephase angle IVTt2, the second sample of the target exhaust phase angleEVTt2, the second sample of the target EGR rate Regrt2, and the secondsample of the basic value of target ignition timing IGb2, by using thetorque characteristics function. Then, the plural intake torquecalculation unit 63 calculates the third sample of the intake ignitioncorresponding torque Trqe3 corresponding to the actual rotational speedNer, the third sample of the charging efficiency Ec3, the third sampleof the target intake phase angle IVTt3, the third sample of the targetexhaust phase angle EVTt3, the third sample of the target EGR rateRegrt3, and the third sample of the basic value of target ignitiontiming IGb3, by using the torque characteristics function.

<Calculation of Intake Torque Approximated Curve>

The relationship between the first sample to the third sample of thecharging efficiencies Ec1, Ec2, Ec3, and the first sample to the thirdsample of the intake ignition corresponding torques Trqe1, Trqe2, Trqe3is shown in FIG. 9. Generally, if the thermal efficiency is constant,the relationship between the charging efficiency and the output torqueis proportional. However, since the thermal efficiency also changes ifthe ignition timing, the VVT phase angle, and the EGR rate change, it isconsidered that it is not proportional relationship strictly. Therefore,approximate precision will be increased if approximated by a quadraticfunction.

Then, in the present embodiment, the intake torque approximated curve isset to a quadratic function as shown in a next equation. The intaketorque approximated curve calculation unit 64 calculates coefficients P,Q, R of respective terms of the intake torque approximated curve whichis set to a quadratic function, based on the intake sample numbers ofthe charging efficiencies Ec1, Ec2 . . . and the intake sample numbersof the intake ignition corresponding torques Trqe1, Trqe2 . . . .

Trq=P×Ec ² +Q×Ec+R  (10)

In this quadratic function, if there are three points of relationshipbetween the charging efficiency Ec and the output torque Trq, the threecoefficients P, Q, R can be calculated by substituting these to theequation (10) respectively and solving simultaneous equations. Forexample, the intake torque approximated curve calculation unit 64calculates the three coefficients P, Q, R using a next equation.

$\begin{matrix}{\begin{bmatrix}P \\Q \\R\end{bmatrix} = {\begin{bmatrix}{{Ec}\; 1^{2}} & {{Ec}\; 1} & 1 \\{{Ec}\; 2^{2}} & {{Ec}\; 2} & 1 \\{{Ec}\; 3^{2}} & {{Ec}\; 3} & 1\end{bmatrix}^{- 1}\;\begin{bmatrix}{{Trqe}\; 1} \\{{Trqe}\; 2} \\{{Trqe}\; 3}\end{bmatrix}}} & (11)\end{matrix}$

The intake sample numbers may be preliminarily set to four or morenumbers, four or more points of the relationship between the chargingefficiency Ec and the output torque Trq are calculated, and by a methodof regression analysis such as the least square method, the coefficientsP, Q, R of respective terms may be calculated.

<Calculation of Target Charging Efficiency Using Intake TorqueApproximated Curve>

As shown in a next equation, the torque intake air amount calculationunit 65 calculates the charging efficiency corresponding to the lowresponse target torque Trqts by solving the equation of the quadraticfunction and using the coefficients P, Q, R of respective terms, as thetarget charging efficiency Ect.

$\begin{matrix}{{{{P \times {Ect}^{2}} + {Q \times {Ect}} + \left( {R - {Trqts}} \right)} = 0}{{Ect} = \frac{{- Q} + \sqrt{Q^{2} - {4 \times P \times \left( {R - {Trqts}} \right)}}}{2 \times P}}} & (12)\end{matrix}$

2-2-6. Calculation of Target Value of Combustion Control State

The torque interface unit 32 is provided with a combustion controltarget calculation unit 66 that calculates a target value of acombustion control state which is a control state of the combustionoperation mechanism. As shown in FIG. 10, the combustion control targetcalculation unit 66 calculates the target value of the combustioncontrol state, by using a combustion control target setting function inwhich a relationship between preliminarily set kinds of drivingconditions and the target value of the combustion control state is set.In the present embodiment, the target EGR rate Regrt, the target intakephase angle IVTt, and the target exhaust phase angle EVTt are calculatedas the target value of the combustion control state; and an EGR ratetarget setting function, an intake phase angle target setting function,and an exhaust phase angle target setting function are used as thecombustion control target setting function.

The combustion control target calculation unit 66 calculates the targetEGR rate Regrt corresponding to the actual rotational speed Ner and thetarget charging efficiency Ect, by using the EGR rate target settingfunction in which a relationship among the rotational speed Ne, thecharging efficiency Ec, and the target EGR rate Regrt is preliminarilyset. In the present embodiment, the EGR rate target setting function isconfigured by map data. The EGR rate target setting function may beconfigured by a neural network.

The combustion control target calculation unit 66 calculates the targetintake phase angle IVTt corresponding to the actual rotational speed Nerand the target charging efficiency Ect, by using the intake phase angletarget setting function in which a relationship among the rotationalspeed Ne, the charging efficiency Ec, and the target intake phase angleIVTt is preliminarily set. In the present embodiment, the intake phaseangle target setting function is configured by map data. The intakephase angle target setting function may be configured by a neuralnetwork.

The combustion control target calculation unit 66 calculates the targetexhaust phase angle EVTt corresponding to the actual rotational speedNer and the target charging efficiency Ect, by using the exhaust phaseangle target setting function in which a relationship among therotational speed Ne, the charging efficiency Ec, and the target exhaustphase angle EVTt is preliminarily set. In the present embodiment, theexhaust phase angle target setting function is configured by map data.The exhaust phase angle target setting function may be configured by aneural network.

2-3. Flowchart

The procedure (the control method of the internal combustion engine 1)of schematic processing of the controller 30 concerning calculation ofthe target ignition timing IGt and the target charging efficiency Ectwill be explained based on the flow chart shown in FIG. 11. Theprocessing represented in the flowchart in FIG. 11 is recurrentlyimplemented, for example, every predetermined operation cycle while thecomputing processing unit 90 implements software (a program) stored inthe storage apparatus 91.

In the step S01, as mentioned above, the driving condition detectionunit 330 implements driving condition detection processing that detectsvarious kinds of driving conditions, such as the actual rotational speedNer of the internal combustion engine and the actual charging efficiencyEcr as the in-cylinder intake air amount information. In the step S02,as mentioned above, the torque control unit 31 implements target torquecalculation processing that calculates the target torque (in thisexample, the low response target torque Trqts, the high response targettorque Trqtf). In the step S03, as mentioned above, the actual torquecalculation unit 55 implements actual torque calculation processing thatcalculates the actual output torque Trqr corresponding to the presentdriving conditions, by using the torque characteristics function. In thestep S04, as mentioned above, the target ignition timing calculationunit 51 implements basic ignition timing calculation processing thatcalculates the basic value of target ignition timing IGb correspondingto the present driving conditions, by using the ignition timing settingfunction.

In the step S05, as mentioned above, the plural ignition torquecalculation unit 52 implements plural ignition torque calculationprocessing that calculates ignition sample numbers of ignitioncorresponding torques Trqi1, Trqi2 . . . which are the ignition samplenumbers of output torques corresponding to the respective ignitionsample numbers of ignition timings IG1, IG2 . . . , by using the torquecharacteristics function. In the step S06, as mentioned above, theignition torque approximated curve calculation unit 53 implementsignition torque approximated curve calculation processing thatcalculates an ignition torque approximated curve approximating arelationship between the ignition sample numbers of the ignition timingsIG1, IG2 . . . and the ignition sample numbers of the ignitioncorresponding torques Trqi1, Trqi2 . . . . In the step S07, as mentionedabove, the approximated curve ignition calculation unit 54 implementsapproximated curve ignition calculation processing that calculates theignition timing corresponding to the target torque (in this example, thehigh response target torque Trqtf), as the target torque correspondingignition timing IGtt, by using the ignition torque approximated curve.

In the step S08, as mentioned above, the target ignition timingcalculation unit 51 implements target ignition timing selectionprocessing that calculates the basic value of target ignition timing IGbcalculated in the step S04 as the target ignition timing IGt when thereis no torque down request by retarding ignition timing; and calculatesthe target torque corresponding ignition timing IGtt calculated in thestep S07 as the target ignition timing IGt when there is the torque downrequest by retarding ignition timing.

In the step S09, as mentioned above, the plural intake ignitioncalculation unit 62 implements plural intake ignition calculationprocessing that calculates the intake sample numbers of the basic valuesof target ignition timing IGb1, IGb2 . . . corresponding to therespective intake sample numbers of the charging efficiencies Ec1, Ec2 .. . which are preliminarily set to plural numbers, by using the ignitiontiming setting function. In the step S10, as mentioned above, the pluralintake torque calculation unit 63 implements plural intake torquecalculation processing that calculates the intake sample numbers of theintake ignition corresponding torques Trqe1, Trqe2 . . . which are theintake sample numbers of the output torques corresponding to therespective intake sample numbers of the charging efficiencies Ec1, Ec2 .. . and the respective intake sample numbers of the basic values oftarget ignition timing IGb1, IGb2 . . . , by using the torquecharacteristics function.

In the step S11, as mentioned above, the intake torque approximatedcurve calculation unit 64 implements intake torque approximated curvecalculation processing that calculates the intake torque approximatedcurve approximating a relationship between the intake sample numbers ofthe charging efficiencies Ec1, Ec2 . . . and the intake sample numbersof the intake ignition corresponding torques Trqe1, Trqe2 . . . . In thestep S12, as mentioned above, the torque intake air amount calculationunit 65 implements torque intake air amount calculation processing thatcalculates the charging efficiency corresponding to the target torque(in this example, the low response target torque Trqts), as the targetcharging efficiency Ect, by using the intake torque approximated curve.In the step S13, as mentioned above, the combustion control targetcalculation unit 66 implements combustion control target calculationprocessing that calculates the target value of the combustion controlstate (in this example, the target EGR rate Regrt, the target intakephase angle IVTt, and the target exhaust phase angle EVTt), by using thecombustion control target setting function.

In the step S14, as mentioned above, the ignition control unit 333implements ignition control processing that determines the finalignition timing SA based on the target ignition timing IGt, and performsenergization control to the ignition coil 16 based on the final ignitiontiming SA. In the step S15, as mentioned above, the intake air amountcontrol unit 331 implements intake air amount control processing thatcontrols the air amount taken into the cylinder based on the targetcharging efficiency Ect. In the step S16, as mentioned above, thecombustion control unit 334 implements combustion control processingthat performs driving control of electric actuators of the EGR valve 22,the intake VVT14, and the exhaust VVT15, based on the target EGR rateRegrt, the target intake phase angle IVTt, and the target exhaust phaseangle EVTt.

Other Embodiments

Lastly, other embodiments of the present disclosure will be explained.Each of the configurations of embodiments to be explained below is notlimited to be separately utilized but can be utilized in combinationwith the configurations of other embodiments as long as no discrepancyoccurs.

(1) In the above-mentioned Embodiment 1, there has been explained thecase where the torque characteristics function and the ignition timingsetting function are configured by the neural network. However,embodiments of the present disclosure are not limited to the foregoingcase. That is to say, one or both of the torque characteristics functionand the ignition timing setting function may be configured by otherfunctions, such as map data and an approximated curve.

(2) In the above-mentioned Embodiment 1, there has been explained thecase where the combustion control target setting functions, such as theEGR rate target setting function, the intake phase angle target settingfunction, and the exhaust phase angle target setting function, areconfigured by map data. However, embodiments of the present disclosureare not limited to the foregoing case. That is to say, each combustioncontrol target setting function may be configured by other functions,such as a neural network.

(3) In the above-mentioned Embodiment 1, there has been explained thecase where the combustion operation mechanisms are the intake VVT 14,the exhaust VVT 15, and the EGR valve 22; the target intake phase angleIVTt, the target exhaust phase angle EVTt, and the target EGR rate Regrtare calculated as the target value of the combustion control state; andthe intake phase angle target setting function, the exhaust phase angletarget setting function, and the EGR rate target setting function areused as the control target setting function. However, embodiments of thepresent disclosure are not limited to the foregoing case. That is tosay, the combustion operation mechanism may be changed depending on thesystem structure of the internal combustion engine, and may be avariable valve lift mechanism, a variable compression ratio mechanism, aturbocharger, a swirl control valve, a tumble control valve, and thelike; the target value of the combustion control state may be a targetvalve lifting amount, a target compression ratio, a target superchargingpressure, a target swirl control valve opening degree, a target tumblecontrol valve opening degree, and the like; and the control targetsetting function may be a function which sets each target value.

(4) In the above-mentioned Embodiment 1, there has been explained thecase where the internal combustion engine 1 is a gasoline engine.However, embodiments of the present disclosure are not limited to theforegoing case. That is to say, the internal combustion engine 1 may bevarious kinds of internal combustion engines, such as an engine whichperforms HCCI combustion (Homogeneous-Charge Compression IgnitionCombustion).

Although the present disclosure is described above in terms of anexemplary embodiment, it should be understood that the various features,aspects and functionality described in the embodiment are not limited intheir applicability to the particular embodiment with which they aredescribed, but instead can be applied, alone or in various combinationsto the embodiment. It is therefore understood that numerousmodifications which have not been exemplified can be devised withoutdeparting from the scope of the present disclosure. For example, atleast one of the constituent components may be modified, added, oreliminated.

What is claimed is:
 1. A controller for an internal combustion enginecomprising at least one processor configured to implement: a drivingcondition detector that detects driving conditions of the internalcombustion engine including in-cylinder intake air amount informationwhich is information of an air amount taken into a combustion chamber; aplural intake ignition calculator that calculates intake sample numbersof basic values of target ignition timing corresponding to therespective intake sample numbers of the in-cylinder intake air amountinformations which are preliminarily set to plural numbers, by using anignition timing setting function in which a relationship betweenpreliminarily set kinds of driving conditions including the in-cylinderintake air amount information, and the basic value of target ignitiontiming is a preliminarily set; a plural intake torque calculator thatcalculates the intake sample numbers of intake ignition correspondingtorques which are the intake sample numbers of output torquescorresponding to the respective intake sample numbers of the in-cylinderintake air amount informations and the respective intake sample numbersof the basic values of target ignition timing, by using a torquecharacteristics function in which a relationship between preliminarilyset kinds of driving conditions including the in-cylinder intake airamount information and an ignition timing, and the output torque of theinternal combustion engine is a preliminarily set; an intake torqueapproximated curve calculator that calculates an intake torqueapproximated curve which is an approximated curve approximating arelationship between the intake sample numbers of the in-cylinder intakeair amount informations and the intake sample numbers of the intakeignition corresponding torques; a target intake air amount calculatorthat calculates the in-cylinder intake air amount informationcorresponding to the target torque which is an output torque requiredfor the internal combustion engine, as a target in-cylinder intake airamount information, by using the intake torque approximated curve; andan intake air amount controller that controls the air amount taken intothe combustion chamber, based on the target in-cylinder intake airamount information.
 2. The controller for the internal combustion engineaccording to claim 1, wherein the ignition timing setting function isconfigured by a neural network, and wherein the torque characteristicsfunction is configured by a neural network.
 3. The controller for theinternal combustion engine according to claim 1, wherein the intakesample numbers are preliminarily set to greater than or equal to threenumbers, and wherein the intake torque approximated curve calculatorcalculates coefficients of respective terms of the intake torqueapproximated curve which is set to a quadratic function, based on theintake sample numbers of the in-cylinder intake air amount informationsand the intake sample numbers of the intake ignition correspondingtorques.
 4. The controller for the internal combustion engine accordingto claim 1, wherein the intake sample numbers are preliminarily set tothree, wherein the plural intake ignition calculator calculates anactual value of the output torque corresponding to actual values of thedriving conditions, by using the torque characteristics function;calculates a value according to a value obtained by multiplying a ratioof the target torque to the actual value of the output torque, to theactual value of the in-cylinder intake air amount information, as atarget corresponding in-cylinder intake air amount information;calculates a value between the actual value of the in-cylinder intakeair amount information and the target corresponding in-cylinder intakeair amount information, as an intermediate in-cylinder intake air amountinformation; and uses the actual value of the in-cylinder intake airamount information, the target corresponding in-cylinder intake airamount information, and the intermediate in-cylinder intake air amountinformation, as the intake sample numbers of the in-cylinder intake airamount informations.
 5. The controller for the internal combustionengine according to claim 1, wherein the target torque is an outputtorque required for the internal combustion engine without consideringretarding the ignition timing.
 6. A control method for an internalcombustion engine comprising: a driving condition detecting that detectsdriving conditions of the internal combustion engine includingin-cylinder intake air amount information which is information of an airamount taken into a combustion chamber; a plural intake ignitioncalculating that calculates intake sample numbers of basic values oftarget ignition timing corresponding to the respective intake samplenumbers of the in-cylinder intake air amount informations which arepreliminarily set to plural numbers, by using an ignition timing settingfunction in which a relationship between preliminarily set kinds ofdriving conditions including the in-cylinder intake air amountinformation, and the basic value of target ignition timing is apreliminarily set; a plural intake torque calculating that calculatesthe intake sample numbers of intake ignition corresponding torques whichare the intake sample numbers of output torques corresponding to therespective intake sample numbers of the in-cylinder intake air amountinformations and the respective intake sample numbers of the basicvalues of target ignition timing, by using a torque characteristicsfunction in which a relationship between preliminarily set kinds ofdriving conditions including the in-cylinder intake air amountinformation and ignition timing, and the output torque of the internalcombustion engine is a preliminarily set; an intake torque approximatedcurve calculating that calculates an intake torque approximated curvewhich is an approximated curve approximating a relationship between theintake sample numbers of the in-cylinder intake air amount informationsand the intake sample numbers of the intake ignition correspondingtorques; a target intake air amount calculating that calculates thein-cylinder intake air amount information corresponding to the targettorque which is an output torque required for the internal combustionengine, as a target in-cylinder intake air amount information, by usingthe intake torque approximated curve; and an intake air amountcontrolling that controls the air amount taken into the combustionchamber, based on the target in-cylinder intake air amount information.